Polymeric materials are widely used in the field of implantable medical devices. For example, polymeric materials such as silicone rubber, polyurethane, and fluoropolymers are used as coating and/or insulating materials for medical leads, stents, and other devices.
Incorporating polymeric materials into implantable medical devices may be done by a variety of methods, depending on the specific application. In some applications, for example, for implantable lead bodies, the polymeric material may be extruded at a temperature sufficient to cause the polymeric material to flow, but not high enough to cause the polymeric material to break down. That is, the material that forms the lead after the extrusion and cooling has largely the same structure as the original polymeric material.
In other applications, it may be desirable to employ a solvent-based deposition process to incorporate a layer of the polymeric material into an implantable medical device. Solvent-based deposition processes include electrospraying, electrospinning, spray coating, dip coating, and force spinning. Essential to all solvent-based deposition processing of polymeric materials is that the polymeric material be in solution while retaining the basic structure of the polymeric material. In some cases, the very properties of strength and chemical resistance that characterize some polymeric materials also make it difficult to manufacture the polymeric material and to form solutions of the polymeric material.
Block copolymers are polymeric materials made of alternating sections of polymerized monomers. A polyisobutylene-polyurethane block copolymer is a polymeric material with many unique and desirable physical and mechanical properties, including thermal stability, chemical resistance, biocompatibility, and gas impermeability, among others. However, these physical characteristics may also make both the manufacturing and the solvent-based deposition processing of the polyisobutylene-polyurethane block copolymer difficult and time consuming. Improvements are needed in the manufacturing and solvent-based deposition processing of the polyisobutylene-polyurethane block copolymer.